unsafe extern "C" fn on_mpv_update(ctx: *mut c_void)Expand description
mpv’s update callback. Runs on an mpv thread, so it does the least possible: flags the state and asks GTK to redraw on the main loop.
Nothing here may block or re-enter the player. The project’s deadlock gotcha applies with full force — this is called from mpv’s own threads.
TRACES: UR-080 | DR-233